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Bengaluru floods a 'man-made' disaster: City needs rainwater harvesting, citizen participation, says water activist

Bengaluru was brought to a standstill on Wednesday when flash floods inundated large parts of the city. However, if the water channels and lakes of Bengaluru had been better maintained, the city may not have suffered such a situation. The city received 12.8 cm of rain in just five hours between Monday night and Tuesday morning, the most rain the city has got for the month of August since 1980.

And as Bengaluru's citizens woke up to find inundated roads and drainage water entering their houses in low-lying areas, India's IT hub came to a thundering standstill.

The rain uprooted trees, twisted electric poles and snapped cable lines in upscale residential areas, disrupting power supply. Civic officials used makeshift boats to rescue stranded residents in some areas, while power outages led to blackouts for hours since early morning.

As it often happens, years of human neglect and indiscriminate exploitation of resources was again responsible for what was eventually termed a natural disaster. Vishwanath Srikantaiah, Bengaluru-based water activist, believes, there were several factors that contributed to the situation.

Firstpost spoke to the noted water activist, researcher and advisor at Biome Environmental Solutions. Here are edited excerpts from the conversation.

While the rain flooded many parts of the city, most affected were South and West Bengaluru. Image courtesy: Facebook/Priya Chetty-Rajagopal

While the rain flooded many parts of the city, most affected were South and West Bengaluru. Image courtesy: Facebook/Priya Chetty-Rajagopal

Torrential rains caused Tuesday's flash floods, but what according to you really caused the chaos and why was the city hit so hard?

Certainly, there were a series of complex reasons involved because of which the city was inundated this way. Firstly, we experienced an unprecedented (amount of) rainfall in a short span of time. The rain was really intense, which is pretty unusual for the city.

Besides this, urbanisation patterns are also to be blamed. We have built up over our lakes and water channels such that the water has nowhere to go.

And we were also simply unprepared. There was no plan in place ahead of the monsoon to counter such a situation.

Flood sensitive zones should have been mapped and people should have been informed, so that they were prepared in a much better way, but this did not happen. There was no communication; people did not even know whom to call when they woke up to the floods. No preemptive steps were taken to deal with this sort of a situation, though we could see that coming.

The precipitation recorded between Monday and Tuesday was three to four times heavier than what was predicted. Is there a need to improve our weather monitoring system?

We have one of the best prediction systems available anywhere in India. The Karnataka State Natural Disaster Monitoring Centre (KSNDMC) has installed around 82 telemetric rain-gauge systems to track rainfall data, and it was being monitored in real time. So there can be simply no excuse for the lack of preparedness.

Monsoons are a timed and well-tracked phenomenon and we knew this was coming. Every year in July-August, we face heavy rains over a short duration of time, and it has become a problem. Efforts taken by the authorities did not suffice.

It was not enough because we should have cleaned up the storm water channels much ahead of the monsoon and the encroachment from wetlands and cachement areas should have been cleared. But we did not have that kind of equipment nor the budget to clean up the water channels completely.

Urban flash floods, the sort we saw in Chennai last year, or in Bengaluru this week, are apparently a more recent phenomenon. Has the rainfall patterns changed , and if yes, what has caused this change?

Yes, flash floods in cities like Bengaluru are definitely a more recent phenomenon and it is mainly because of three reasons. First is the change in the rainfall patterns, but we are also building way too much and building indiscriminately.

Thirdly, we are actually receiving heavier precipitation than we are used to, ie, we get more rainfall in short spurts.

The reason behind this change in rainfall pattern could be attributed broadly to what you call climate change. However, urbanisation in itself is a phenomenon that alters the climate and rainfall patterns. The urban heat island effect — which implies the urban centres tend to be warmer than their surroundings due to pollution and various other reasons — causes the build-up of rain clouds on the city.

The city too has changed tremendously over the past two decades, How has this change impacted the natural flood management system?

Yes, the city has changed. We have expanded beyond its limit, and it's all a result of rampant urbanisation. Between 2002 and 2016, the city's population has exploded to 11 million.

There was never a flood monitoring system in the city so to speak, but we had natural and man-made lakes and well-linked storm water drains. But tanks and lakes, which collected surplus storm water, have now been built upon and drains connecting them are encroached. There is no space for the runoff water to collect or to percolate through the soil to recharge ground water. The result you see is that the water fills up your homes and your roads.

Then there is no plan or system in place for solid waste management, which is another parameter that aggravates the flood situation. Most of the garbage that we produce ends up in the drains, and it chokes the water channels, so when there is excessive rainfall, the capacity of our water channels is reduced. There is no way that the water can escape.

How can we mitigate the effect of such floods, is there a solution in sight?

Definitely. We need to see the floods situation as an advantage. There is a need to implement rainwater harvesting on the principle of retention and detention of water. If we can equip each and every site to harvest at least 60 mm of rainwater in the event of rain, the flood situation can be hugely mitigated.

It can be done either by crating storage tanks (retention) or recharging the groundwater through aquifers. Had we harvested the rainwater that fell on Bengaluru this week (at an average of 100 mm over 1,250 sq km), we could have had 125,000 million litres, which is 89 days' worth of supply from the Cauvery river. Rainwater harvesting alone can make a substantial difference.

Besides this, we also have to be innovative with our thinking. There is a need to come up with ways to protect our lakes and maximise recharge of groundwater table through natural means. There are lakes, like the Bellandur lake, that are practically dead due to pollution. There is no other option but to clean it up, treat the water. We should reimagine these lakes as wetlands instead of a waterbodies. That is the best way forward.

Moreover, Bengaluru needs to prepare for more rain than average and of higher intensity. The city, at any given time, should be prepared to absorb and control 180 millimetres of rainfall in one day, even though it gets only about 60 millimetres of rain in one day.

These would be long term changes, which need policy intervention and the political will. Would you suggest any immediate measures to arrest the damage?

If we are concerned with immediate results, then the damage has already been arrested, because it's not raining anymore, and the water has receded. However, to avoid a situation like the one we saw this week, we would have to uproot encroachments and reclaim the city's lakes and drains. There is no way around it. We must also immediately clean up the existing water channels and desilt our water tanks and reservoirs.

Apart from the policy changes you mentioned, what kind of citizen initiatives would you suggest to make the change happen?

Citizens should involve themselves and map all these areas that were flooded this time. They should get involved with the corporators in each ward and draft out a strategy to deal with the situation when it comes around the next time. People should also be made aware of the role they can play in mitigating the effects of flood. Thereafter, rainwater harvesting and solid waste management too need citizen intervention and cooperation. All this change must come from the people.

Updated Date: Aug 17, 2017 21:16 PM

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